Many measuring apparatuses, in which a pulsed light is irradiated onto a biological object, a photoacoustic wave generated from inside the biological object is received by a probe, and the forms and functions inside the biological tissue are displayed as images, have been proposed in medical fields. This technology is called “photoacoustic tomography (PAT)”. In such an apparatus, the intensity of the light irradiated into the biological tissue attenuates while propagating inside the biological tissue due to absorption and scattering, hence only very little light reaches the depth of the tissue. As a result, photoacoustic waves are generated inside the biological tissue, and electric signals (photoacoustic signals) converted by the probe become weak. To prevent this, a Q switch is installed in the light source to perform rapid oscillation, so that the quantity of pulsed light is increased, and a higher quantity of light reaches the depth.
An apparatus, in which a plurality of light sources are installed so as to increase the quantity of light that reaches the depth of a subject by simultaneously irradiating pulsed light onto the subject from both sides thereof, has also been proposed in Japanese Patent Application Laid-Open No. 2010-017426.
An example of the conventional measuring apparatus will be described with reference to FIG. 12A. FIG. 12A shows a configuration of the conventional measuring apparatus. The reference numeral 81 is a biological tissue, that is a subject, 82a and 82b are pulsed lights, and 87 is a light absorbing area existing inside the subject. The light absorbing area refers to an area which absorbs energy of the pulsed light, and generates a photoacoustic wave efficiently, and an example is a blood vessel. 88 is a photoacoustic wave generated from the light absorbing area 87, 85 is a probe for converting the photoacoustic wave 88 into an electric signal, and 86a and 86b are plate members for securing the subject 81. A direction from the probe 85 to the subject 81 is a Z direction, a vertical direction from top to bottom is a Y direction, and an X direction is a horizontal direction which is orthogonal to the Z direction and the Y direction. If the pulsed lights 82a and 82b are irradiated onto the subject 81, the photoacoustic wave 88 is generated from the light absorbing area 87. This wave is converted into an electric signal (photoacoustic signal) by the probe 85, and is then converted into a diagnostic image by an electric circuit, which is not illustrated, and is output. The timings of irradiating the pulsed lights 82a and 82b and the timings of receiving the photoacoustic signals are controlled by a controller, which is not illustrated.
A laser processing apparatus which can control the emission timings of a plurality of pulsed lights has also been proposed in Japanese Patent Application Laid-Open No. 2000-343256. Japanese Patent Application Laid-Open No. 2000-343256 discloses a method for adjusting the emission timings of two pulsed lights by changing a start timing of a pulse laser oscillation.